1. Technical Filed
The present invention relates to an ink jet head and its manufacturing method, and an ink jet printer.
2. Related Art
In recent years, the performance of ink jet printers has advanced to levels that can provide a high picture quality equivalent to the picture quality of photographs. This has been achieved by increasing the number of nozzles of an ink jet head and reducing the amount (volume) of a discharged liquid droplet to enable ultra-high-density drawing (printing). Furthermore, in addition to ultra-high-density printing, there are great demands for higher printing speeds. For meeting both demands, the number of nozzles is an important factor and the greater the number of nozzles, the more advantageous the configuration is for higher density and higher speed printing. Among ink jet heads of a system in which the volume of a cavity is changed by a piezoelectric element to jet (eject) a droplet, those with ultra-high-density have 6-8 rows, each of the rows including 80 dpi×2 of nozzles. However, by simply increasing the number of nozzles, the size of the head becomes larger. In this respect, in order to reduce the size of the head and provide nozzles in an ultra-high density, the cavity needs to be made smaller.
FIG. 9 shows a cross-sectional view of a structure of a conventional ink jet head. Reference numeral 210 denotes a nozzle plate, reference numeral 211 denotes nozzles (discharge openings), reference numeral 220 denotes a Si substrate, a reference numeral 230 denotes a vibration plate, and reference numeral 240 denotes piezoelectric elements. Cavities 221 of the recording head are formed through patterning the Si substrate 220 by wet etching or dry etching, which is then bonded with the nozzle plate 210. The height (depth or size) of the cavities 221 and the thickness of each side wall 222 are designed such that the vibration plate 230 has a proper displacement.
However, as the cavities 221 are formed with a higher density for achieving ultra-high-density printing by the ink jet head, the thickness of the side wall 222 inevitably becomes thinner, and as a result, the side wall 222 would likely resiliently deform by the operation of the piezoelectric element 240. Thus, the volume of each of the adjacent cavities 221 changes due to the deformation, and as a result, it becomes difficult to maintain the correct discharge amount, and there is a possibility that the image quality of the printed matter may deteriorate.
The present invention has been made in view of the problems of the conventional technology, and one object is to provide an ink jet head that can effectively suppress operational interferences among adjacent cavities, and is capable of ultra-high-density and high-speed printing, and its manufacturing method. Also, it is an object of the present invention to provide an ink jet printer that is equipped with an ink jet head that is capable of ultra-high-density and high-speed printing.